Field of the Invention
A film chamber is a test chamber with at least one flexible wall portion made e.g. of a film material. A typical film chamber comprises two film layers laid one against the other around the test object so as to entirely enclose the test object. After having received the test object, the film chamber is hermetically sealed and evacuated. Thereafter, the pressure change in the film chamber volume is monitored in the region outside the test object, where a pressure increase is considered an indication of a leak in the test object. As an alternative to monitoring the pressure in the film chamber volume, it is also possible to monitor the flexible wall portion, where a change in the flexible wall portion or the film, respectively, may indicate a leak. Such a method is known from DE 10 2012 200 063 A1.
With a test object having a gross leak it is a problem that upon evacuating the film chamber, the test object is simultaneously evacuated as well through the gross leak. Measuring the pressure increase for detecting a leak after the evacuation of the film chamber must fail in this case. A gross leak is considered to be a leak allowing a volume flow through the leak that draws a substantial portion of the free volume in the test object during the pump-down time.